The electrochemical production of oxygen from water has been studied extensively as a component of water-splitting schemes which can be used in the sustainable generation of hydrogen by electrolysis of water and a renewable energy source, such as sunlight. The water oxidation half-reaction may also serve as the anodic half reaction coupled with other aqueous electrochemical reductions, such as electrodeposition of metals and/or organic electroreductions. In these schemes, higher efficiency of water oxidation afforded by a catalyst reduces the overall amount of energy needed for these processes. Although some oxides and organometallic compounds of 2nd and 3rd row transition metals, such as Ru, Rh, Ir, and Pt are among the most active water oxidation catalysts known, their low abundance and the high cost of such metals are substantial obstacles to their widespread application.
Cobalt oxides and the recently developed cobalt phosphate/phosphonate/borate compounds (e.g., Co-Pi) offer significantly more affordable and scalable alternatives. These cobalt catalysts are not without their drawbacks, however. Their primary method of synthesis is through electrodeposition. These catalysts are prone to degradation at the high currents required for commercial water electrolysis, as well as in buffers that do not contain a significant concentration of phosphate, or other strong proton acceptor.
There exists a need for catalysts that do not suffer from the limitations described above.
Therefore, it is an object of the invention to provide catalysts, particularly oxidation catalysts, that do not suffer from the limitations described above and methods of making and using thereof.